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Where
volcanic eruptions repave part of the seafloor and rejuvenate hydrothermal
venting, the process of biological colonization can be studied starting
from a "clean slate". Colonization of new vent sites progresses
very rapidly, because vent species are adapted to rapidly changing and
ephemeral habitat. On the 1998 lava flow at Axial Volcano, the vent-specific
species that colonized most quickly included tubeworms, scaleworms, palmworms,
limpets, and snails. Vent sites were already beginning to be colonized
on the 1998 lava flow only 7 months after the eruption. However,
most new vents had few individuals, and adjacent vents usually had completely
different species (the first arrivals). Over time the vents have exploded
in the numbers of individuals and species present, and the difference
between vents has diminished. For example, in 1998 only about half of
the species known from Axial had reached the new vents. But, by the summer
of 1999 (12 months later) almost the whole Axial species pool had successfully
colonized, and by the summer of 2000 abundances at the new vents rivalled
those at most longer-lived vent communities (1000's of individuals per
vent).
All the
new vents on the 1998 lava flow are diffuse vents. On lobate surfaces
of the 1998 lava flow, vent fluid emanates from the conical depressions
between lava lobes (such as at Circ vent, near Castle). These sites are
probably underlain by lava pillars, which act a fluid conduits from the
bottom to the top of the lava flow. On sheet flow surfaces with collapsed
areas, diffuse vents such as at Marker 33 occur along cracks in lava crust.
Here, the vent is more elongate and colonization is distributed along
the crack.
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